1. Field of the Invention
The present invention relates to a relevant-information retrieval system. More specifically, the system is used in an environment where heterogeneous databases are united, and it presents or teaches information on databases which administer information items relevant to information being currently searched for, to a searcher for the information, thereby to meet the subconscious search requests of the information searcher. The invention relates also to a program recording medium in which a program for incarnating the relevant-information retrieval system is stored. Besides, it relates to a method for retrieving such relevant information items.
2. Description of the Related Art
In recent years, very large numbers of heterogeneous databases have come to be connected through a computer network such as the Internet. Further, information items have come to be very often provided by individuals. When information is searched for with a conventional retrieval technique under such an environment, inevitably the efficiency of retrieval lowers drastically. It has therefore been required to build up a new retrieval technique for use under such an environment.
A conventional retrieval system has been premised on searching its own databases.
Under such a premise, the retrieval system has been so constructed that information sources (records) are analyzed so as to be correlated, and the information sources relevant to the information source of a request for search are searched on the basis of the correlation, thereby to realize the search for relevant information.
However, in such a case where the databases connected to a network are to be searched, the technique of the conventional retrieval system as stated above expends an enormous processing time period on the correlations of the information sources due to an explosive increase in the number of the databases, resulting in the problem that the search for the relevant information is substantially impossible.
Besides, the relevant information is often closed in a database category to which the information belongs, and the search for the relevant information cannot be always realized. Therefore, the retrieval system has the problem that the relevant information cannot be heuristically presented to the information searcher.
Moreover, in the case where the databases connected to a network are to be searched, the number of the relevant information items increases suddenly, and it becomes necessary to limit and present the relevant information items corresponding to the request of the information searcher. Nevertheless, it has not been considered at all in the conventional retrieval system that the relevant information items are limited as is necessary.
On this occasion, it is also thought out to adopt a method wherein the relevant information items are presented individually. This method, however, poses the problem that the relations of the information items are difficult to be understood or grasped.
Further, in the case where the databases connected to the network are to be searched, secondary information items on the keywords of these databases are not defined. By way of example, when the information searcher accesses the database retaining the relevant information, he/she fails to input a mandatory keyword. This causes the problem that the database is forced to execute an exceptional process, or that an access cost increases.